Railway signaling system



Dec. 12, 1944. w. F. ZANE EIAL RAILWAY SIGNALING SYSTEM Filed July 18,1941 5 Sheets-Sheet l INVENTORS I amifZme and GevzgelllBau lzpzm.

THbYH ATTORNEY Dec. 12, 1944. w. F. ZANE ET AL RAILWAY SIGNALING SYSTEMFiled July 18, 1941 3 sheets-Sheet 2 ww ww Inn $4 pq 'uun INVENTORSlUzZlzamEZaneand g w- Z 4 THEIR ATTORNEY 5 Sheets-Sheet 3 INVENTORSl'lliamFZcme and B yGeorgelflBaufbman THHH ATTORNEY Dec. 12,1944. w. F.ZANE ETAL RAILWAY SIGNALING SYSTEM Filed July 18, 1941 under thecustomary control of switches.

Patented Dec. 12, 1944 UNITED E15 PAT ENT OFFICE.

2,364,840 RAILWAY SIGNALING" SYSTEM. 7

William. Zane, La- Grange, 111;, and George.

Baug-hman;v Swissvale, Pa., assignors to. The Union Switch and. SignalCompany, Swissvale, 2a., a corporation. of Pennsylvania 3 ApplicationJilly 18, 1941', Serial No." 402-,9'06

i Claims. (01.246-33 Our invention relates to a railway; system adaptedfor use in track stretches where trafiic moves in both directions overa; single track.

It is an object of our inventionto provide an improved signaling systemin'which the signals controlling both" directions of'trafiic' aregoverned byasingleline circuit.

A further'obj'ect of ourin'ventibn is to provide an improvedsystem' ofthe type described which employs coded energygin the'linecircuits andwhich is arranged so that a cross betweenthe linewires will not produceafalseclear signal.

Another object of our invention is to provide an improved signalingsystem of the type described.

We shall describe twoforms-of' railway' signaling system embodying ourinvention, and" shall then point out the novel features thereof inclaims. i

In the drawings,

Fig. I is adiagram consistingofFigs. IA and 1 13 and showing a stretchof railway track equipped with one formof signaling system embodyingour-invention, and i Fig. 2' is a diagram consisting of Figs. 2A and 2Band showing a stretch of railway track equipped witha modified form ofsignaling system embodying our invention.

Similar reference characters refer to similar parts in both views.

Referring to Fig. I of the drawings, there is shown therein astretch ofsingle track railroad over which traflic moves in both directions. Tofacilitate description of the equipment it will be assumed that theright-hand end of the track stretch is east and that the left-hand endthereof is west. I The track. stretch includes passing. sidings whichare located at appropriate intervals and permit traffic to be divertedfrom the main track Two such passing sidings are shown and aredesignatedXandY.

The rails I and" 2 of the track stretch are divided by insulatedjoints 3into'track sections designated 2T, 3T, 4T, 5T, etc. Each of the tracksections is provided with a track circuit including a track batteryconnectedacross the section rails at one end of the section, and a trackrelay, designated TR with a suitable prefix, connected across thesection rails at the other end of the section.

Eastbound trafiic through the track stretch is governed by a pluralityof trackway signals desthrough the trackstretch is governed by signalsdesignated 1S, 5S and 35., The signals shown are of the color lighttype, but-it" should be 'un'- derstood' that the invention is notlimited to the use' of signals of this type andthat any appropriate formof waysides'ignal well'known. in the art may be employed. Eachof thesesignals, has a green or: clear lamp G', a" yellow or" caution lamp Y,and a red or..stop lamp. R. The signals 88 and 38 at the entrancejen'dsof the passing sid ings have'upper portions'whi'ch includ'ethe green,yellow and: red lamps as illustrated in the drawings, while thesepsigrialsmay'also have low'er portions, not shown, governing movement oftrains from the main track onto the passing sidin'gs. i. j L

The diagram which forms the drawings shows the means for controllingthessignals 4S, 58,, 6S and 18;. The means for controlling thesignals 3Sand B'S'is not aipartofv this. inventionand has not been shown, andthese signals may be controlled in any appropriate manner well known inthe art.

In most cases the contacts associated with each relay are shown in thedrawings directly under the relay winding. However, in, a few instancesno energy is supplied.

ignate'd 48, BS and 88, while westbound traffic.

the relay contacts are separated from the relay winding, and where thisis done. the relay with which the contactis associated is indicated byappropriate reference characters located-directly above the contact.

In the system provided by this invention the signals 48 and: 58. arecontrolled over a line cir.-.-

cuit J which includes line wires. 20' and.2|, "whil1e' signals 6S and 1Sare controlled over a line circuit K which includes. linewires Hand-23;

Each signal location is provided; with a suitable sourceof directcurrent such as. a storage battery, not shown, the terminals. of whichare designated B and C. y i

The equipmentisshown in the condition which it assumes when the trackstretch is vacant. At this time the coding relay JCR'Li's. supplied withenergy of 180 code frequency fromv a code transmitter ICT over a circuitwhich includes front 7 contact 25 of relay 3TB. This, energy consists ofenergyimpulses a minute which are-sepa rated'by periods of equalduration during which When. the coding. relay JCR 'contacts 26 and21.,establish a circuit tosupply impulses of master code. energy to theline circuit J At this time. as sections 2T and 31 is. picked up, its

through front contact 28 of relay 3D and front contact 26 of codingrelay JCR to line wire 20, while terminal C is connected through frontcontact 29 of relay 3D and front contact 21 of coding relay JCR' to linewire 2| so that the master code supplied to line circuit J is of normalpolarity.

This master code energy is supplied over the line circuit and throughback contacts 30 and 3| of impulse relay JIR to line relays SP and EN.

The line relays 4P, P, GP and IP are of the stick polar type havingcontacts which are moved to their normal positions, as shown, on thesupply of energy of normal relative polarity to the relay winding, andto their other or reverse positions on the supply of energy of reverserelative polarity to the relay winding. The contacts of these re layswhen moved to either position remain in that position until the relaywinding is supplied with energy eifectiveto move the relay contacts totheir other position.

- The line relays 4N, 5N, 5N and IN are of the biased polar type andrespond to flow of energy in the windings thereof in one directiononly.

The polar line relays P control the connection from the line circuits tothe line relays N so that if the contacts of the polar relays respond tochanges in the polarity of the current supplied to the line circuits,the relays N will be connected with the line circuits in such mannerthat energy 'will flow in the relay windings in the direction effectiveto pick up the relay contacts.

The arrangement of the relays P and N is not the tw portions oftheprimary winding of de-,

coding transformer EDT are alternately energized and energy is inducedin the secondary winding of this transformer. The energy induced in oneof these secondary windings is supplied through the resonant rectifierunit 5RU to the relay. 5H. 7

The unit RU is constructed in the manner well known in the art and isarranged so that it passes sufiicient energy to pick up. the relay 5Hwhen and only when the relay 5N. is responding to energy of 180 codefrequency.

As contact35 of relay 5H is picked up and as contact 36 of relay SP isin its normal position, the circuit of the green lamp G of signal 58 iscomplete and this lamp is lighted so that the signal 58 provides itsgreen or clear indication.

The energy induced in the other secondary winding of the transformer EDTis supplied to the impulse relay JIR. The relay JIR is of a type whichresponds to energy of one polarity only and the various parts of theequipment are arranged so that energy of the polarity efiective to pickup thecontacts of ,the relay JIR is supplied to 'the relay on release ofthe contacts of relay. 5N.

Accordingly, during the supply of an impulse of master code the contactsof relay JIR are released, While during the off periods in the mastercode the contacts of relay JIR pick up to disconnect the line circuitfrom the relays SP and 5N, and to establish a circuit to permit impulsesof feed-back energy to besupplied to the line circuit. The contacts ofrelay JIR when picked up remain picked up for a, short time interval,but become released and reestablish the circuit of the relays 5P and 5Nbefore the start of the next on period in the master code.

When the contacts ofrelay JIR are picked up, a circuit is established tosupply an impulse of feed-back energy to the line circuit J As sectionsBT and IT are unoccupied, the relay SE is picked up so that the impulseof feed-back" energy is of normal polarity.

At this time terminal B is connected through back contact '38 of relay58R, front contact 39 of relay BTR, front contact 40 of relay 6H, andfront contact 30 of relay JIR to line wire 20, while terminal C isconnected through front contact 42 of tact of the relay 4N rectifies theenergy supplied from the secondary winding of transformer 4DI t relay41-1. As a result, contact 44 of relay 4H is picked up and establishesthe circuit which includes normal polar contact 45 of relay 4P forsupplying energy to the green lamp G of signal 4S so that this lamp islighted and conditions signal 48 to provide its green or clearindication.

From the foregoing it will be seen that when the track stretch isvacant, master code energy of positiveor normal polarity and codefrequency is supplied to the west end of the line circuit J andconditions signal 58 to provide its clear indication, while during theoff periods of the ;master code impulses of feed-back energy of positiveor normal polarity are supplied to the east end of the line circuit andcondition signal 48 to provide its green or clear indication.

The equipment for controlling signals 68 and 7S operates in the samemanner as that for controlling signals 4S and 5S, and as the trackstretch is vacant, signals 6S andflS are conditioned to provide theirgreen or clear indications. At this timemaster code energy of 180 codefrequency and normal polarity is supplied to the east end of linecircuit vK, while feed-back energy of normal polarity is supplied to thewest end of line circuit K. Theoperation of this equipment issubstantially the same as that associated with line circuit J and adetailed explanation of its operation is unnecessary.

Operation of equipment on movemenrt of a train through the track stretchFor purposes of illustration it will be assumed that an eastbound trainpasses through the track stretch. When this train enters section 2T,track relay 2TB, releases and interrupts the circuit of relay 3D so thatits contacts 28 and 29 release and change the master code supplied toline circuit J from normal to reverse polarity. This causes the polarcontacts of relay 5P to shift to their reverse positions so that contact36 interrupts the circuit of the green lamp G and establishes thecircuit of the yellow lamp 'Y of signal 5S. This will warn a westboundtrain of the approach of the eastbound train.

On this change in position of the contacts of relay 5P the connectionsfrom the line circuit to asefac'eo' relay N are changed so thateventhough=the polarityof the energy suppliedto the line circuit J'is-reversed, energy continues to flowln" the same direction through therelay; winding. Accordingly, therelay'SNcontinues to follow code sothatenergy is supplied through the decoding transformer 5DT to the relay 5Hand to tlie'impulse relay JIR. Ifhe relay 'JIR, therefore, continues tocause impulses'oi feed-back energy of normal polarity to be'supplied tothe'line circuit .1 so'that signal is continues to provide its green orclear indication. i

As relay 5H remains picked up, the "feedback energy supplied to linecircuit K continues tube of normal polarityrand signal 18 continues to;display its green or clear indication.

When the train advances intosection 31, track relay 3TH releases and itcontact interrupts the circuit for supplying energy of 180 codefrequencyto the coding relay- JCR and establishes a circuit including backcontact l1 of' relay 33R for supplying energy of 75 code frequency" tothe coding relay JCR. .AS a result; thecontacts 26 and 21 of relayoperate at-the lower frequencyand master code energy of 75 codefrequency. is supplied to the line circuit Jtso' that relay-5N-iollowsthis code and causes the relay 'JIR to supply feedeback energytoathe. line circuit to maintain the display of the iclear indication bsignal 48.. V y

Whenrelay 5N is following energy of 75 code frequency, too little energyis supplied through the resonant unit-iRU'to pick up the relay 51-32.

This relay, therecre,zreleases and Jitsi contact 35 establishes thecircuit 'otthe red or stop lampiR. oiv signal 58, while its contacts 48and. 49 cut on? the supply of "feed-back energy" to line circuit K ascontact 32 of: relay 5SR;is released. rThls relay for supplying-direrational stick relay 38R, and when the contactsofthis relay'pickup, its contact i l establishes a 'circiut 'to'manitain the relayenergized-aslo ge track -relay3 I'R, is released When the contacts'oirelay 38R. are picked up,-its contact I 1 interrupts the supplyoi'energy of 75 code frequencytothe coding relay 'JCR whlle its contactestablishes the circuit to supply energy 180 code frequency to thisrelay. The change iii-the rate of operation of relay JCR iswithoutconsequence; however; as

long: as section'fiIor 5T is'oc'cupied'since master code. is preventedvfrom being supplied over the line-circuit when. these sections areoccupied. 1

When the train advances into section 51?, track :relay' S'IR releasesandi'its contacts 58 and interrinit': and. short circuit 'the linecircuit J.

. At this time fmaster code-energy oflfld code frequency and normalspolarity" continues torbe supplied :toxthe east. end line circuit K. sothat signal is: continues'toeprovide itsxgreen :or

clearindication'. V,

. In addition, on release-cf relay STR its: contact 53" releasesbutbecause cizthe prior release 10f contact, .62' oftrelay 5H:the-pick+upcircuit ofrelay 58R is not established and: contact 63 ofthis relay'remains'released;

"When the trainrenters section 6T, track relay 811R releases. and cutsnil-the supply of master causes relay 'IHatO release so thatitscontactBl establishes the circuit of the red lamp R (ii-signal TS to thereby;prevent a. westbound Ztrairr from advancing beyond signallS.

When the train-adyances into section 41; track relay 4TR releases andits contacts 52 and-53 interruptthe line circuitJ, andthereby preventthe supply of energy to line relays JP and 4N, andalsotorelaysiP and 5N.

" Accordingly,- relay GN' releasesand energy code energyto relays-6Pand:N, whileit also prevents the supply: of ffeedebackfr energy'totheline-circuit'K. hIn addition, on release of track relay 6TB; itscontacts short circuit the; portion of. line circuit K associated linerelays; 1F

and IN to prevent improperenergization of these relaysas'explainedabovey is no: longer supplied through the decoding trans.-iormefSDTand thevresonant unit BRU to relay 6H, and this relay-releasesand its contact '64 signal 6S. 7

establishes the circuit of the red-IlampRrof The relayBH-isisomewhatslow'in releasing and a itscontactsremainv-pickedupforaacperiod sub- When the supply of master codeto line circuit J is interrupted, relay-5N ceases to follow code andenergy is no longer supplied to relay JIR so that this relay ceases tooperate andiimpulses of "feed- In addition, on release of the contacts52 and a 5-3 of track relay-4TB they short circuit "the portion of theline circuit which isoconnectedto line relays Panel 4N during the'releasedperindsof the contacts 26 and zlr-of coding relay JCR. As

this portion. ofthe line circuit is short circuited there istic-possibility that. the relay 4N will be energized if, because ofacross or: other-condition, energy is improperly suppliedtothis'p'ortion of the line circuit. Therelay 4N, thereiore, remainsreleased and energy is not supplied through the transformer IDT torelay! so that relay AI-I'will remain released and maintain the displayof a stop indication by signal: 48.

- .On release of relay 4TB its contact 55' com pletes the circuitincluding baclccontactiis of sequent :to release of the contactsof:relay 6TB. As. a result on entranceof a train into section 6T; itraclcrelay liTR'releases and" its contact 65 establishes a pick-upcircuit iorrelayiSR. This circuit includes front contact of relay 'GH.

soon as relay 68R picks up; its contactBG establishes a stick circuit'for, energizing the relay after release of relay EH; :When rreiayliSR'v is picked up, its contact it permits supply of feedback" energyof reverse polarity-to the line cir-' cuit J while'relay 6H is-released;while. contact 68 .01? relay 68R prevents the supply of: feedback energyto line circuit Kt When the train advancessinto section TI; track relayt'IR releases andfladditionally interrupts and: short circuitsline'circuitK.

When the trainvacates section 3T, 7 track relay 3TB picks upand-itscontact 56=intzerruptathe circuit of the relay 3SR'.so,'thatthisrelayreleases,

while contact-25 0f relayTl-R: establishes a circuit tonsupplyuenergy ofcode-:trecuencyto the coding relay JCR. y e In addition, when-relay3TR-picks up the c'irv cult of the-relay 3D complete and the contacts28' and 29 of this: relay'picl; up so that the. mas

ter code: supplied to the line circuit 'Jis. again: of 180 codefrequency and normal rel'ative polarity.

when the: train advancesiar enough to vacate sections 4.1" and ST; linecircuit J is againcomplete and the: maste code supplied to-the linecircuit feeds to the line relays SP and 5N and 1 signal 5Sis againconditioned to provide its green or clear indication.

contact 69 of relay 8D.

Asa result of code following operation of relay 5N, impulses of energyare supplied to relay JIR.

At this time relayGH is released, while, as xplained above, relay BSR ispicked up. As lon When the train advances far enough to vacate section6T, relaylBTR picks up and it contact 39 establishes the circuit forsupplying impulses of feed-back energy of reverse polarity to linecircuit J. At this time terminal B is connected through back contact 38of relay 58R, front contact 39 of relay BTR, back contact 40 of relay6H, and'front contact 3| of coding relay JIR to line .Wire 2|, whileterminal 0 is connected through tact 11 of relay GP to light the yellowor caution lamp Y of signal 68.

cause the green or clear lamp G of signal to be lighted;

On picking up of relay BI-I its contacts 40 and 42 change the ffeed-back energy supplied to line circuit J from reverse to normal polarity. On

back contact 42 of relay 6H, front contact 61 of I relay GSR, and frontcontact 30 of relay J13 to 1 line wire 20. As a result of the supply'offeed back energy of reverse polarity to line circuit J,

the contacts of relay 4P are shifted to their right- -hand or reversepositions, while energy is supplied through the decoding transformer 4DTto relay 4H so that its contact 44 picks up and cooperates withreverse'polar contact 45 of relay 4Nto light the yellow or caution lampY of signal 68.

, When the train advances into section 8T, track 1 relay BTR- releasesand interrupts the circuit of 3 relay 8D so that its contacts 69 and 10release and change the polarity of the master code en ergy supplied toline circuit K. g In addition, on release of track relay 8TB its contactll completes the pick-up circuit of relay 1 88R. This circuit alsoincludes back contact 12 p of track relay I'IR, while, when relay 8SRpicks up, its contact [3 establishes a stick circuit to i maintain therelay energized as long as track 1 relay BTR is released.

On release of track relay 8TB its contact 14 1 interrupts one circuitfor supplying energy of 180 code frequency to coding relay KCR, whilecontact 16 of relay 8SR establishes another circuit to supply energy ofthis code frequency to this relay. Accordingly, the coding relay KCRcontinues to operate at the 180 code rate.

Similarly, when the train advances into section 1 9T, track relay 9TB.releases and interrupts the circuit of relay 8D to maintain it released.

When the train advances far enough to vacate section 1T, track relay ITRpicks up and completes line circuit K so that master code of 180 codefrequency and reverse polarity is supplied over the line circuit to theline relays GP and 6N. The energy supplied to the line circuit is ofreverse polarity as relay 8D is released and terminal B of the source isconnected to line Wire 23 i through back contact 10 of relay 8D, whileterminal C is connected to line wire shift to their reverse positions,while relay 6N follows the code and energy is supplied through thedecoding transformer 6DT and the resonant unit BRU to pick up the relay6H. Accordingly,

the contact 64 of relay 6H interrupts the circuit In addition, onrelease of track relay 8TB the f signal BSis conditioned by means notshown to display its red or stop indication.

this change in the polarity of the feed-back energy supplied to linecircuit J the polarcontacts of relay 4P are shifted to their left-handor normal positions and contact establishes the circuit of the green orclear lamp G of signal 48.

When'thetrain advances far enough to vacate section 8T, track relay 8TB,picks up and its contact 1| interrupts the circuit of relay BSR, while:its contact 14 establishes a circuit to maintain code supplied to linecircuit K from reverse to normal polarity. On this change in thepolarity of the master codesupplied to line circuit K the polar contactsof relay 6P are shifted from their reverse to their normal positions andcontact 11 establishes the circuit of the green lamp G of signal 63. Atthis time'there is no change in the polarityof the feed-back energysupplied to line circuits J and K so that signals 48' and .15 continueto 'display'their green orclear indications. g

The operation of the equipment onmovem ent of a Westbound train throughthe track stretch is substantially the same as for movement of aneastbound train through the track stretch and a detailed explanationthereof is unnecessary.

It Willbe seen also that when the track stretch v is vacant, .mastercode energy of 180 code frequency and positive or normal polarity issupplied to each line circuit at the end thereof adjacent the headblocksignal to control the intermediate signal, while feed-back energy ofpositive or normal polarity is supplied to the line circuit at the endthereof adjacent the intermediate signal to control the headblocksignal;v

When a train enters the overlap section at the leaving end of a passingsiding, the master code supplied to the adjacent line circuit is changedfrom 180' code frequency to code frequency.

This energy is not effective to control the intermediate signal sothissignal is caused to display its stop indication, but this energycauses feed- From the foregoing "it will be seen that the' .invention isdirected to use on single track back" energy tov be generated sothatithe headblock signal in frontof thetrain continuesto display itsclear indication In additiomonthis the display of a .clear indication bythe intermediate signalin front of'the train,

When the train passesthe intermediate signal, the other line circuit isinterruptedso that the intermediate signal is placed at stop. -When-thetrain vacates the stretch in; the rear of the intermediatesignal,;.fmaster.-; code-of 180 frequency is again supplied over theline circuit associated with that signaland causestheintermediate signalfor the opposite directionof traffictoagain display its'clearindication. The supplyof feedback energy to this line circuit continuesto:be cuton until the train -.vaca tes .the tracksection in advance ofthe mtermediatewsignal so-Zthat the headblock signal in the reart-of:the "trainicontinues to display its stop indication. 1

When the train doesyacate thetrack section in advance of theintermediate vsignai, feed-- back energy of reverse polarity. issuppliedto the line circuit in the rear. of the intermediate signal so that the,headblock signal ;in the rearof th train displays its cautionindication;

When the train advances-beyondthe signallat the entrance end of :thenextpassiug siding and vacates the section :in'the rear of zthiscsignal,master code of 180 codefrequency and reverse polarity is suppliedvovertheiline circuit totcon dition the intermediate, signal inthezrearzotthe train to display its caution signal,.-,and:to-.ca11se the feed-backenergy suppliedto the other: line circuit to be changedfromzreversetoxnormal polarity and thereby cause .the.unification. dis-.played by theheadblock signal in:thesrear of that intermediatesignaltobe changedfrom'cam tionto clear. .In addition; at thisxtime teed .backenergy of normalpolarity'isl supplied over the line circuit immediatelyin the rear ,of "the train to. condition the headblockrsignalin the rearof the train and controlling \traffic .in the oppositev direction todisplay itssgreen or. clear indication.

Construction of modification shown in Fig. ,2 In Fig. 2 of the drawingsthereis ishown-a modified form at signaling system which may be employedin place of that shown in Fig, 1.1 The system shown in Fig. 2 is similartorthatshown in Fig. 1, but difiers therefrom .inthat. thecodetransmitters are located at the: intermediate sis? nal locationinsteadof .at thesheadblock signals. Accordingly, in the system shown in Fig.2fmaster code is supplied from the intermediatesignals to theheadblocksignals, whileffeedeback energy is supplied inthe.opposite.direc'tion-..

The modification shown-in Figtz, .likethat shown in Fig. 1, employsmaster 'codeiof two codev frequencies, while theequipment at theheadblock locations :is arranged fSQ .thatit will respondto only Qnepfthesefrequencies to;c0n I dition the associatedrsignalto display aproceed signal to display a proceed indication. a

indication. However, master? code of either frequency will causefeed-back energ'yto be developed. and thereby. cause the intermediate Inthe drawings showing the system of 2 most of, the relay contacts areshown directly below the relay windings, .but in. some instances thecontacts-are shown separated from the windings. Where this is done, therelay with which thecontact is associatedis' indicated byapp-ropriate.reference characters locateddirectly above the contact.

The equipment of Fig. 2 is shownin the condition which it assumes whenthe trackstretch circuits J and K. i

is vacant. At thisvtime the trackrelays ar all picked up andline '{circuits J and K are both complete. a

Atthis time energy of 180 code frequency is suppliedto the coding relayJCR over the circuit which is traced. from terminalB through the contactof code transmitter I80C?I ,,f ront contact 1 no of relay 15H, frontcontact 401 l of track relay 6TH, and back contact I0? oi relay 58R..Inlike traced from terminal B through the contact .of

code transmitter IBOC'I, front contact I05 of-relay 5H, front contactI06 of trackrelay 5'IR,-.and'

back contact I01 of relay-8BR. Accordingly, the coding relays JCR andKCR operate to supply master code oilBOpode irequencyto the line As. therelays 6H andiiH are picked up, the master codes are of normal polarityso that signals 43 and 1S] are both; conditioned to provide their greenor clear indications. I

As a result of code followingoperation ofthe relays 4N and1N,.impu1sesofenergy are supplied to the impulse relays JI R .andKIR andthese relays operate to cause impulses of feedback energy to'be suppliedto the line circuits J and K. .As. the'relays ,3D .and BD are picked up,the freed-back energy is cfnormal polarity 'When an eastbound train ienters ,sectiondiT, track relay ZTR releases and interrupts the cir'-.

cuit of relay 313 so that relay '3D releasesand changes the polarity ofthe feed-back; energy supplied to line circuitJ from normal to reverse.

. On this change in the polarity 01" the feedback energysupplied.tojline' circuitJ the con- -tacts of relay 5P are shifted totheirreverse position and cause signal5S to display its yellow or cautionindication. At {this tirne.,.rela y 15H remains picked up.andmaster"code oinormal polarity continues to be supplied to,1 in circuit Ksothat signal IS continues ,to provide its green or clear indication.

When thetrain a amant SeQtionf3T.1,track relay 3TB. reieases and' itscontact ,lljn interrupts the circuit. forhjsupplying feed back3 energyto line circuit.J i so that relay, 5H;releases andilig'hts the redorstoplamp Br f ,signal.;5.s:.' .Inaddition, on release of. relay 5H"itslcontacts .H' II and H2 change the polarity oi the mast'efcodesupplied to linecircuit Kirom normal toreverse polarity; whi1e...as.-aresult of the release of con:- tact I05 ofrelay liiH the "fmaster.codesupplied to line circuit Kishhanged irldm 180.1:0 .120 codefrequency. The circuit for vsutnolyingQenergy to the coding relay,KCR.is traced from B through the contact of code transmitter I'ZU C'I backcontact H4 of relay 58R, back contact I of relay 5H, front contact I06of relay 5TB, and back contact l0! of relay GSR.

On this change in the frequency of the mas-i ter. code supplied to linecircuit K insufiicient energy is supplied through the resonant unit TRU.

to keep relay 1H picked up and this relay releases and causes signal isto display its redor stop indication to therebyprevent a westbound trainfrom advancing beyond the passing siding Y.

Th master code of 120 frequency sup-plied over line cir'cuitK causesfeed-back energy to relay 4TB. releases and its contacts interrupt linecircuit J to thereby cut off the supply of mas Accordingly, the mastercode supplied to line ter code over this line circuit to the line relays4Pand 4J with the result that relay 4H releases and establishes thecircuit of the red or stop lamp R of signal 48.

:- In addition, on release of the track relay 4TB its contacts shortcircuit the portion of the line circuit J connected to the linerelays 5Pand 5N "to prevent "operation ofthese relays in the eventenergy'isimproperly' supplied" to the line,

circuit J.

-When the train advancesinto section 5T, track relay 5TB. releases andits contact I06 interrupts the circuit traced above for supplying energyof 120 code frequency to coding relay KCR and establishes anothercircuit for supplying energy of this frequency to relay KCR so that thesupply of master code of 12 0"co-de frequency to line circuit K ismaintained and feed-back energy continues to besupplied to the linecircuit to maintain the display of .a clear indication by signal 63.

When the train advances into section 6T, track 'relay'STI'R releases andinterrupts line circuit K.

and thereby causes signals 18 and 68 to provide their red 'or stopindications.

At this time contact I I5 of relaytTR establishes the pick-up circuitfor relay 68R. "This circuit also includes front contact I16 of relay5H, while on pickingup of relay BSR its contact I ll establishes a stickcircuit which includes back contact H6 of relay 6H.

circuit J is .of 120 code frequency. This energy is ineffective tocontrol signal 4S so that this signal continues to display its stopindication. This energy does produce operation of the impulse relay JIRso that feed-back energy is supplied to line circuit J. As'relay 3D ispicked up, the feedback energy isof normal polarity andsignal 58 isconditioned to display its green or clear indication. Y

When the train advances far enough to vacate section 6T,track relay 6TB.picks up, but relay 6H remains released while relay BSR remains pickedup by energy supplied over its stick circuit. On picking up of relay BTRits contact l0! interrupts the circuit traced above for supplying energyof 120 code frequency to coding relay JCR, and establishes a'circuitincluding front contact H9 of relay BSR for supplyin energyof'180 code frequency to coding relay JCR so that master code of 180code frequency is supplied to the line circuitJ. As relay 61-1 isreleased;t-his energy is of reverse polarity-s0 that signal 48isconditionedto' provide itsyellow or caution indication.

- 7 'When the train advances into section 8T, track relay 8TB. releasesand-interrupts the circuit of relay 8D, while contact [2! of relay 8TBcompletes the pick-up circuit of relay 88R. This circuit also includesback contact 122 of relay lTR,

while when relay BSR picks up its contact I23 establishes a stickcircuit to keep the relay energized as long as relay 8TB. is released. I

In addition, onrelease of track relay 8TRthe signal BS is conditioned bymeans not shown to display its red or stop indication.

vOn release of relay B'I'R its contact I25 interrupts one circuit forvsupplying feed-back energy to line circuit K,-but on picking up of relay88R When the train advances into section 1T, track j lishes the circuitto permit feed-back energy to be supplied to line circuit J. However,master code is not supplied over the circuit'at this time so thatimpulse relay JIR remains released and.

feed-back energy is not supplied to line circuit J.

' .When the train vacates sections 4T and ET, the track relays 4TB. and5TB pick up and complete. line circuit J to permit master" code to besupplied over this circuit. At this time energy of 120 code frequency issupplied to coding relay JCR over the circuit which includes backcontact I0] its contact I26 establishes another circuit to permit thisenergy to be supplied. Accordingly, when the train vacates section ITand track relay 1TB. picks up to complete'line circuit K, master code issupplied over this line circuit so that impulses of energy are suppliedto impulse relay KIR and thisrelay causes"feed-bac k energy to besupplied to the line circuit. As relay 5H-is picked up, the mastercodesupplied to line circuit K is of normal polarity'and conditions thesignal is to display its green or clear indication, while as relay 8D isreleased, the feed ba'ck energy supplied to line circuit 1; is ofreverse polarity so that signal 6S displays its yellow or cautionindicatiOn. I

When the train vacates section II and feedback energy is supplied overline. circuit K so that relay 6H 'picksf up," its contacts change themaster code energy supplied to the east end of line circuit J fromreverse to normal'polarit'y.

Accordingly, "the contacts of relay 4? shift. from theinreverse'totheir'normal positions and interrupt the circuit of the yellow lamp Yand establish the circuit of the'green lamp G of signal 4S. 1

Fromathe' foregoing it, will; be'seerrgthata the; modification shown:Fig 2; .like: that shown in Fig. 1, provides means employing a;singlelin'e circuit to control the signals for-bothzdizrections oftraffic in antrack stretch, The modifications shown in Fig. 2; like;thatshowrr in:Fig-., 1,,em ploys master code: in the line circuit tocontrol they signals for; one directionuof traffic; and'employsfeed-back codein the same line circuit 1 to control the signalsforthe other direction of traffic. The; polarity. of the master andfeedeb'ack, energy is controlled to thereby provide, two dis-- tinctiveproceed indications for each direction of traffic.

In the system shown in Fig.- lwhen a train enters the overlap section atthe leaving end: ot a passing Siding", the frequency offithe fmaste codeis changed so that the intermediate /signal, governing trafiic in theopposite direction is placed at stop, but feed backif energy is suppliedto maintain the display of anproceed indication by the headblock signalin front of the train.

In the system shown in Fig. 2 the master code is supplied at the end ofthe line circuit adjacent the intermediate signal location. When a trainenters the overlap section, master code continues to be supplied overthe line circuit to maintain the display of a proceed indication by theheadblock signal in front of the train, but the supply of feed-backenerg over the line circuit is cut off to thereby place the intermediatesignal for the other direction of traiiic at stop.

In the system shown in Fig. 2 when th train advances into the tracksection in the rear of the intermediate signal, the frequency of themaster code supplied to the line circuit in advance of the intermediatesignal is changed. This causes the headblock signal at the leaving endof the passing siding in advance of the train to display a stopindication, but it also causes feed-back energy to be supplied to theline circuit to maintain the display of a proceed indication by theintermediate signal in front of the train.

Although we have herein shown and described only two forms of railwaysignaling system embodying our invention, it is understood that variouschanges and modifications may be made therein within the scope of theappended claims without departing from the spirit and scope of ourinvention.

Having thus described our invention. What we claim is:

1. In combination, a stretch of railroad track having a pair of trackrails over which tramc moves in both directions, the rails of the trackstretch being divided by insulated joints into a plurality of tracksections including an intermediate section having at one side a firstsection and at the other side a second section, a, first signalgoverning movement of trafilc from the first section into theintermediate section,- a second signal governing movement of trafficfrom the second section into the intermediate section, a line circuitsubstantially coextensive with and controlled by traffic conditions insaid intermediate section, means governed by trafiic conditions in saidfirst section for supplying to the line circuit master code energy of afirst or second code frequency and of one or the other polarity, meansresponsive to master code energy of either frequency and either polaritysupplied over said line circuit for supplying feed-back energy to saidline circuit, means responsive to master code energy of one codefrequency only supplied over said line circuit and selectivelyresponsive to the polarity and mean responsive to feedebaclmenergy uplied-rover saidalinecircui't for. controlling saidr first signal 2. In,combinatiom; a stretch of railroad having a pair I of: track I rails=--over wh ch 1 3 119;

moves inboth= directions -the rails of the-track,

stretch being dividedby insulated j oints ,--i-n -to a;

in said, first: section for supplying to the line cir-n, cuitmaster codeenergy; of a first-c or :a second code: frequency andof one or th otherpolaritw means responsive to master code energy of either frequency andeither polarity supplied over saidline circuit for supplying feed-backenergy to said line circuit, means governed by trafiie conditions insaid second section for controlling the polarity of the feed-back energysupplied to said line circuit, means responsive to master code energy ofone code frequency only supplied over said line circuit and selectivelyresponsiveto the polarity of such energy for controlling said secondsignal, and means responsive to feed-back energy supplied over said linecircuit and selectively responsive to the polarity of such energy forcontrolling said first signal.

3. In combination, a stretch of railroad track having a pair of trackrails over which trafiic moves in both directions, the rails of thetrack stretch being divided by insulated joints into a plurality oftrack sections including an intermediate section having at one side afirst section and having at the other side a second section, a firstsignal governing movement of trailic from the first section into theintermediate section, a second signal governing movement of traffic fromthe second section into the intermediate section, a line circuitsubstantially coextensive with and controlled by trafic conditions insaid intermediate section, means for supplying to said conductors mastercode energy of a first code frequenc when said first section is vacantor is occupied by a train leavin said intermediate section and forsupplying to said conductors master code energy of a second codefrequency when said first section is occupied by a train advancingtowards said intermediate section, means governed by occupancy of saidfirst section and controlling the polarity of the master code energysupplied to said line circuit, means operated by master code energy ofsaid first code frequency only and selectively responsive to thepolarity of such energy for controlling said second signal, meansresponsive to the supply of master code energy of either frequency andeither polarity for supplying feed-back energy to said line circuit,means governed by occupancy of said second section and controlling thepolarity of the feed-back energy supplied to said line circuit, andmeans operated by feed-back energy supplied over said line circuit andselectively responsive to the polarity of such energy for controllingsaid first signal.

4. In combination, a stretch of railroad track having a pair of trackrails over which trafiic moves in both directions, the rails of saidtrack stretch being divided by insulated joints into a of suclr energyfor controllingilsaid, second signals;

first, a' second, a third and a fourth section, a first signal governingentrance of trains into the second section from the first's'ection asecond,

signal governing entrance of trains into the second section from thethird section, a line circuit substantially coextensive with andcontrolled by trafiic conditions in said second section,-means forsupplying to said conductors master code energy of a first codefrequency when said first section is vacant or is occupied by a trainleaving said second section and for supplying to said line circuitmaster code energy of a second code fre quency when said'first sectionis occupied by a train advancing towards said second section; meansgoverned by occupancy of said first section and controlling the polarityof the master code energy supplied to said line circuit, means operatedby master code energy of said first code frequency only and selectivelyresponsive to the polarity of such energy for controlling said secondsignal, means responsive to the supply of master code energy of eitherfrequency and either polarity over said line circuit and controlling acircuit over which feed-back energy may be supplied to said linecircuit, means 'efiective only when said third and fourth sections arevacant or are occupied by a train leaving said second section to permitfeedback energy to be supplied to said line circuit, means effectivewhen said third section is vacant and said fourth section is vacant oris occupied by a train leaving said third section to cause the feed-backenergy supplied to said lin circuit to be of normal polarity, meanseffective when said third section is occupied by a train leaving saidsecond section to cause the feed-backener-gy supplied to said linecircuit to be of reverse polarity, and means operated by feed-backenergy supplied over said line circuit and selectively responsive to thepolarity of such energy for controlling said first signal.

WILLIAM F. ZANE.

GEORGE W. BAUGHMAN.

